High performance polymers (HPP) are a fast growing portion of the engineering polymers market. These polymers offer excellent performance under harsh operating conditions by virtue of their high temperature stability, chemical resistance, high tensile properties, and abrasion resistance. However, existing polymers all display compromises in certain attributes while excelling in others. In general, thermoplastic HPP are either semi-crystalline or amorphous with the former typically offering superior chemical and abrasion resistance and the latter superior thermal resistance and mechanical toughness. The most common semi-crystalline HPP are polyphenylene sulfide, liquid-crystal polyesters, and polyether ketones, and the most common amorphous HPP are polyether sulfones and thermoplastic polyimides. These polymers are typically filled with glass fiber, carbon fiber, graphite, and other materials as reinforcements to improve their tensile properties, dimensional stability, and wear resistance.
One particularly new type of HPP is self-reinforced polyphenylene (SRP), an amorphous polymer with many of the attributes of the semi-crystalline polymers. SRP offers a unique combination of tensile properties, abrasion resistance, chemical resistance, and thermal stability. The key to its high performance is the rigid-rod phenylene backbone which makes further fiber reinforcement unnecessary. The polyphenylene backbone can be substituted with phenylketone groups to render it amorphous and allow for thermal processing. For example, Wang and Quirk, Macromolecules, 1995, 28 (10), p. 3495, disclose that poly(2,5-benzophenone) is thought to be amorphous due to the head-tail disorder introduced in the polymer backbone during polymerization of 2,5-dichlorobenzophenone and that the degree of disorder has an effect on the glass transition temperature (Tg) of the polymer.
Since the ketone version of SRP is already amorphous, but retains many attributes of a semi-crystalline HPP, a sulfone version of SRP, such as poly(2,5-diphenylsulfone) (PDS), has the potential to expand its set of properties without compromising those normally due to semi-crystallinity and expand its utility into applications currently meet only by high performance polyimide products. However, the polymerization conditions that are successful for poly(2,5-benzophenone) do not produce high molecular weight PDS.